Flexible plate heat exchangers with plate flexing controlling means



Feb. 8, 1966 c. F. ROSENBLAD 3,233,665

FLEXIBLE PLATE HEAT EXCHANGERS WITH PLATE FLEXING CONTROLLING MEANS Filed Aug. 2, 1965 2 Sheets$heet 1 I N VEN TOR.

ATTORNEY 1966 c. F. ROSENBLAD 3, 3

FLEXIBLE PLATE HEAT EXCHANGERS WITH PLATE FLEXING CONTROLLING MEANS Filed Aug. 2, 1963 2 Sheets-Sheet 2 INVENTOR. KhPTK/FQSE/VBL ,40

BY aw/ 11% ATTOR NE .3

United States Patent 0 FLEXIBLE PLATE HEAT EXCHANGERS WITH PLATE FLEXING QONTRGLLING MEANS Curt F. Rosenbiad, Princeton, NJ. Rosenblad Corp., 1276 6th Ave, New York 20, NY.) Filed Aug. 2, 1963, er. No. 299,514 '7 Claims. (Cl. 165-166) This invention reiates to flexible plate heat exchangers, especially those whose plates are pressed with dimples of uniform height throughout, and is particularly concerned with means for controlling the flexing of such heat exchanger plates.

In flexible plate heat exchangers the heat exchanger plates or walls between the channels will flex so that when the pressure on the medium in one set of the channels is greater than that in the other :set the walls containing the medium under pressure will flex outwardly, thereby narrowing the space in the other set of channels. It has been found desirable to limit the extent to which such walls may flex lest the metal of the walls becomes fatigued .to such an extent that they will eventually fail. Various expedients have been employed for controlling this flexing.

The initial expedients tried for controlling flexing involved the use of spacer members or studs between the plates which were constantly in engagement so that little, or no, deflection of the plates could take place. This had various drawbacks, such as the setting up of blocks in the channels preventing any action to clear away material which might be caught by such blocks, or channel obstructions. This arrangement was superseded by those in which, although spacer members are provided, gaps were still left between the spacer members and plates opposed thereto so that though some flexing of the plate could take place before being stopped by the spacer members, the paths open up periodically.

One most effective means for achieving this is the use of so called dimple plates wherein the flexible plates have embossings formed to uniform extent in opposite directions with respect to a central plane of the plate and in accordance with a uniform alternating pattern throughout the plate. The extent or height of those embossings or dimples is such that with the plates properly assembled in a stack for the forming of the heat exchanger, opposed embossings from adjacent plates, when all plates are in relaxed condition, will be aligned with and close- 1y approach each other, but will leave a small gap between them. These gaps close up when opposed plates are stressed toward each other. Thus when unstressed, or stressed away from each other, the dimples of opposed plates will be separated throughout so that fluids can flow freely between them and any material that has collected where the dimples have come into engagement will be washed away.

In spite of the material improvement introduced into this art by the utilization of dimple plates having uniform spaces between the dimples throughout the heat exchange area, another factor has to be taken into consideration. That is control of the flexing so that the plates may not flex as much towards their borders as they do in their middle positions. Otherwise, undue bending and consequent failure of the plates will take place in the bordering areas. Again, various expedients have been suggested for providing the variable spacing required. With regard to dimple plates it has been proposed to vary the height of the dimples from the borders toward the center of the plates. This, however, is impractical, expensive and does not provide a true solution to the problem having regard to the cost of the size graduated pressing tools needed, variations in thickness of the metal itself, etc.

This invention is, accordingly, concerned with a simple 3,233,665 Patented Feb. E), 1966 ice economical way to accomplish the desired variable spacing While still employing dimple plates having dimples of uniform height. This is accomplished in accordance with the invention by adding spacer members to one side of the sheet to overlie the heads of the dimples and be secured thereto. The spacer members vary in height from the thickest adjacent the borders of the sheets to the thinnest towards the intermediate portion and, in fact, may be dispensed with entirely in an intermediate area of each plate. Additionally, spacers of a diiferent type may be employed in the portions of the channels between the plates which communicate with the inlet and outlet openings for the fluids being put in heat exchange relationship.

It is, accordingly, a principal object of the invention to improve upon the operation of flexible plate heat exchangers.

Another object is to improve upon the functioning of and preserve the strength of dimple plate flexible plate heat exchangers.

Still another objecL is to effect such improvements with regard to dimple plate heat exchangers, while still forming such plates in uniform manner.

A further object is to provide such improvement by mere additions to otherwise uniform dimple plate constructions.

A still further object is to provide such improvements while keeping the interference with flow through the panels at a minimum.

Further and more detailed objects will in part be pointed out and in part be obvious as the description of the invention taken in conjunction with the accompanying drawing proceeds:

In that drawing:

FIG. 1 is a part elevation, part sectional view of a flexible plate heat exchanger to which the improvement of the invention is applied, which elevation is exploded by the showing of an upper portion in vertical section without any particular showing of heat exchanger plates but illustrating the communication of the inlet and outlet ports with the channels, equipped with variable spacer means in accordance with the invention.

FIG. 2 is an enlarged showing of the fragmentary portion of a pair of heat exchange-r plates as seen in the intermediate sectioned portion of FIG. 1 illustrating the condition that exists when pressure on the channels is balanced.

FIG. 3 is a view similar to FIG. 2 but showing the position of the plates with overpressure in one of the channel systems.

FIG. 4 is an enlarged fragmentary elevation of a heat exchanger plate equipped with spacer strips in accordance with the invention as seen in the lower elevational portion of FIG. 1.

FIG. 5 is a fragmentary elevational view of the specially formed portion of the heat exchanger plate in alignment with one of the ports as seen in the lower left hand portion of FIG. 1; and

FIG. 6 is a vertical section taken on line 66 of FIG. 5 and looking in the direction of the arrows.

The heat exchanger to which the invention is applied, as here illustrated and as indicated at i, is generally of a rectangular formation with its longer dimension extending vertically, and with the depth between its front and back faces depending upon the number of channels desired. Such a heat exchanger is typical of those in which flexible heat exchanger plates in accordance with the invention would be employed in spaced side by side relationship while extending throughout the height and width of the exchanger. Such plates so positioned establish channels therebetween for alternately receiving the fluids to be put in heat exchange relationship.

The heat exchanger 1 has a top plate 2, a bottom plate 3, front and back cover plates 4 and 5, and pairs of inlet and outlet ducts adjacent the extreme corners, as shown at 6, 7, 8 and 9. Those ducts may be paired up in various ways, depending upon whether the flow is concurrent, countercurrent, etc. as is known in the art. It is of course, understood that one pair of ducts is in communication with one set of the channels between heat exchanger plates, while the other set of ducts is in communication with the other set.

As already pointed out, the flexible heat exchanger plates 10 employed in the invention construction are in the nature of dimple plates with a plurality of them being employed in spaced side by side relationship, as illustrated in the intermediate section in FIG. 1, and in fragmentary manner in FIGS. 2 and 3. The dimples, 11, in the form of equally spaced and alternately pressed embossings of the plate material extend from opposite sides of the plane 12 of the plate in accordance with a uniform pattern, as best seen in FIG. 2. These plates have edge portions 13 surrounding them which normally lie in the plane of the plate and the outer parts of which are sealingly secured in fixed spaced relationship by some suitable means. In this instance such means take the form of U bars, generally indicated at 14, which open outwardly, have their bases 15 serving as the spacer members between the plates, and have their sides in welded to those outer parts of the edge portions to provide strong joints sealed against leakage. These U bars extend all around the peripheries of the plates with the exception of the positions where the channels between pairs of plates need to be put in communication with their respective ducts, such as 6, 7, 8, 9. Thus for communication of one pair of ducts, one set of U bars is omitted throughout the nozzle opening area to allow fluid to flow into and out of one set of alternate channels. Likewise, in the duct opening area for the other pair of ducts, the path of the first set of channels is closed off by its U bars, while the path to the second set is opened by the elimination of the U bars throughout such area. Such alternate channels are indicated at 17 and 18 in FIG. 3.

From the sectional showing in PEG. 1 and more clearly from the large fragmentary showing in FIG. 2, it will be seen that dimples lit formed out of the dimple plates 19 are of the same height throughout the plates and regardless of the side of the plates to which they extend. Thus their flattened top portions 19 are, in all instances where the plates are in relaxed condition, the same distance from the center plane 12 of the plates. If this condition were allowed to prevail with the plates assembled leaving a uniform distance 26 between the opposed dimple tops 19, overpressure in one or the other of the channels 17 or 13 would cause all of the dimple tops throughout the plate areas bordering the channels under lower pressure to come into engagement, as indicated at 18 in FIG. 3. This, however, would be an undesirable condition, for substantial localized bending of the plates would take place in the edge portions 13, which, particularly in the case of channel switching or pressure switching between channels, would soon cause failure of the metal in such portions. However, such an economical and desirable approach towards controlling the flexing of the very worthwhile thin plates used in flexible plate heat exchangers is embodied in the use of embossed dimple plates that the path to a real solution of the problem lies thruogh the utilization of dimple plates and the elimination of their drawbacks. This is achieved by the construction of the invention in a simple and economical manner.

From the showing in the lower elevation portion of FIG. 1 and also in FIGS. 24, it will be seen that the invention solves the problem by the application of spacer strips of various thickness to the tops 19 of one set of the dimples. These spacer strips may extend throughout the full length,

or height, of the heat exchanger plates, even extending through the portions of the channels where the same are in communication with their respective orifices. However, the preferable construction is one where the strips merely extend to the orifice areas with other spacer members devoid of any likelihood of obstructing the flow in and out of the channels being employed in those areas, as will be pointed out hereinafter.

Considering together then the showings in the lower portion of FIG. 1, with FIGS. 2-4, it will be seen that the column of dimples 11 extending to the same side of each plate closest to the edge portions 13, have spacer strips 27 lying across their fiat tops 19. These spacer strips are suitably secured as by welding to the tops U and, at this position closest to the plate edge, are of a thickness so as to leave very little room for flexing of one plate with respect to the other at this position. Thus from the FIG. 2 showing, which illustrates the condition which exists when two plates from an assembly are mounted in relaxed condition with even pressure on both sides, the strip 27 carried by the lower of the two plates leaves only a small space 28 between its upper surface and the lower surface of the dimple top 19 of the adjacent plate. This space which is hardly noticeable is illustrated at 28.

Moving to the right in FIG. 2, it will be seen that the next spacer strips 25 are of less thickness than the strips 27 so that a greater space as is left for the flexing of the plates. Similarly, and moving further toward the right, the next spacer strip 23 is of still thinner material, leaving a larger space 24, while, finally, the next spacer strip 21 is the thinnest and leaves the largest flexing space 22. From here on, and moving further to the right, it will be seen that there is no spacer strip overlying the next set of dimple tops 19. Then, by reverting to FIG. 1, it will be seen that this last condition prevails all the way across the intermediate portion of the heat exchanger, with the utilization of spacer strips commencing again in reverse order at the other side of the intermediate portion, starting first with the strip 21 and increasing to the strip 27.

It will, of course, be understood that these spacer strips are only employed on one side of each flexible plate and that they lie in opposed relationship to the dimple tops extending towards them from the adjacent plate. They bridge across from one dimple top 19 to the next, so interfere but little with the ilow of fluid inasmuch as there are flow paths above and below them between the dimples.

FIG. 3 illustrates the condition that exists where overpressure is present in one of the sets of channels illustrated at 17, whereupon the plates bordering such channels are flexed outward away from each other. This increases the previous space 28 between the spacer member 27 and its opposed dimples to the larger space 28a. The space above the spacer plate 25 is increased to the space 26a. That above the strip 23 is increased to 24a and that above the strip 21 to 22a. Additionally, the normal space between the tops of the dimples 1? in the intermediate portion of the plate is increased from the space shown at 20 in FIG. 2 to that shown at 2dr: in FIG. 3.

The additional spacing in the set of channels 17 provided for by the closing up of the spaces in the channel 1%, wherein all of the spacer strips 21-27 are shown as in contact with the flat tops 19 of the dimples on the opposed plate, while, even at the right hand end where no spacer strips are present, the dimple tops 19 are shown as having come together.

It is, accordingly, readily apparent that the desired control of the flexing and distribution of the stress is achieved in simple straightforward manner in accordance with the invention, while still taking advantage of the desirable strengthening and spacing characteristics of the uniformly embossed dimple plates.

As a non-limiting illustration of an appropriate arrangement in accordance with the invention, let it be assumed that the space 20 existing in relaxed condition between the dimple tops 19 in FIG. 2 be 1.5 mm. Accordingly, it would be appropriate to form the spacer strip 27 of material of 1.3 mm. in thickness, normally leaving a small space at this position of .2 mm. The thickness of the spacer strips would he graduated down from this, with the spacer strip 25 being .9 mm., the spacer strip 23 being .5 mm. and the spacer strip 21 being .2 mm., leaving respectively spaces 26 of .6 mm., 24 of 1.0 mm., and 22 of 1.3 mm. On the full flexing of one pair of plates, as illustrated in FIG. 3 away from each other where they border a channel, such as 17, the spaces between their spacer strips and opposed dimple tops would of course be increased by the amount gained in the closing up of the spaces in the intermediate channels. The spaces between dimple tops throughout the intermediate section where there are no spacer strips would be doubled. When considering the graduated increase in spacing from the plate edges to the intermediate portion, it will be quite apparent that the bending moment imposed on the section 13 has been reduced to a minimum and distributed most gradually throughout the inward extension of the plates.

Though a graduated arrangement of four spacer strips has here been shown and described, it is of course to be understood that such number of strips with such graduation is purely for illustrative and not for limiting purposes, inasmuch as the strip arrangement employed would be dependent upon the particular condition existing in the particular heat exchanger.

Considering now the condition that exists at the positions where the channels are opened to communication with the inlet or outlet orifices, it is to be understood that for greatest economy and simplicity of construction spacer strips, such as 21437 should be continued throughout the full length of the plates 10, including extending across such communicating areas. However, the likelihood, particularly at the inlet position, of foreign matter that might be present in the fluid catching on the strips instead of flowing past them makes it preferable to employ spacers differently formed and differently positioned in these areas.

Referring now to the lower left-hand portion of FIG. 1 and FIGS. 5 and 6, here, the spacers, instead of being in the form of continuous strips bridging across from one dimple top to the next, are in the form of separate individual elements for each dimple secured to the dimple tops. For convenience these will be referred to as riders. They are formed as strip elements which are oriented in the principal direction of flow of the heat exchange fluid in alignment with the inlet and outlet orifices. Such riders seen at 36, 31, 32 and 33 are graduated in the same manner so there are as many different ones as there are different graduated strips 27-21. They control the flexing of the heat exchanger plates in their areas the same as is done by the elongated strips in the major portion of the extent of the heat exchanger.

Though the riders 3il33 vary in thickness, being graduated down from the thickest at 30 to the thinnest at 33, they all have the same outline when viewed in plan (FIGS. 1 and 5). The riders lie partly up the inclined sides of the dimple as seen at 26a, and then terminate in the portions 30b overlying the flat top 19 of the dimple. The sets of riders 31, 32 and 33 are similarly positioned with respect to their dimples having portions comparable to the portions 301') and 300 but it is believed that a detailing of all these parts is unnecessary for an understanding of the invention.

The riders are preferably welded to the dimples at one or more points, such as one in the portion 30a and another in the portion 30b, and it is of course to be undelistood that each plate is equipped with riders on only one side. Since the respective thicknesses of the dimples in the several columns are respectively the same as the thicknesses of the strips 27-21 their portions, such as 30b, overlying tops 19 of the dimples provide the same spacing with respect to the next adjacent plate as do the strips 27-21. Furthermore, while a particular form of rider and a particular securement of the same to the dimple plates is here shown and described, it is of course to be understood that such is for illustrative and not limiting purposes. The riders may be differently formed and differently positioned, and, like the strips 27-21, they may be graduated differently or of a different number differently graduated, depending on the requirements of the particular heat exchanger.

From the foregoing it is believed to be readily apparent that the invention construction materially improves upon and enhances the operation of flexible plate heat exchangers, particularly those of the lamella type employing dimple plates. Furthermore, though the embodiment described in the foregoing and shown in the accompanying drawing is the presently preferred manner of putting the invention into practice, it is to be understood that certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In plate heat exchangers, a plurality of flexible heat exchange plates of substantially uniform size and shape, said plates being assembled in alignment in spaced parallel relationship and forming sets of alternating channels for the passage of diiferent media in heat exchanging relationship therethrough, said plates being formed with embossings providing a uniform pattern of rows of projections extending a uniform distance from opposite sides thereof, the rows of projections extending parallel to the edges of said heat exchanger plates, means for securing said plates together with said embossings each projection from one plate being in alignment with an oppositely extending projection on the next adjacent plate, and spacer means secured to the tops of the embossings in the rows thereof bordering the edges of said plates on one side of each of said plates, said spacer means of suc cessive rows decreasing in thickness in the direction from the edge of said piates toward the center thereof.

2. Plate heat exchangers as in claim 1, said spacer means being formed as elongated strips extending substantially from one end of said plates to the other thereof.

3. Plate heat exchangers as in claim 1, said spacer means being formed as short strips of material extending in transverse direction with respect to said plates and each engaging a single embossing.

4. Plate heat exchangers as in claim 1, said spacer means at portions of said plates adjacent the ends thereof being short strips of material extending in. transverse direction with respect to said plates and each engaging a single embossing and said spacer means for the portion of said plates extending between said end portions being elongated strips each overlying a plurality of said plates extending between said end portions being elongated strips, each overlying a plurality of said embossings.

5. In flexible plate heat exchangers, a plurality of dimple plates having dimples embossed out of the material thereof extending in uniform patterns and at a uniform height in rows in spaced rows parallel to the longitudinal side edges of the plates from opposite sides of the central plane of said plate, said dimples having flat tops, means for securing said plurality of plates in alignment in spaced parallel relationship, with said flat tops of the dimples of said rows from adjacent plates being disposed overlying each other in aligned spaced relationship and spacer strips extending substantially throughout the length of said plates to control the flexing of said plates, each dimple from one plate being in alignment with an oppositely extending dimple on the next adjacent plate, said spacer strips lying across and bridging from the top of one dimple to the top of the next and being secured thereto, there being a series of said spacer strips in parallel relationship secured to one side of each of said plates and said spacer strips of said series diminishing in thickness in the direction from the edge of said plates toward the center thereof.

6. In flexible plate heat exchanger construction, a plurality of thin flexible heat exchanger plates of substantially uniform size and shape, said plates being assembled in alignment in spaced parallel relationship and being forming sets of alternating channels for the passage of different media in heat exchanging relationship therethrough, said plates being formed With rows of ernbossings in the form of dimples extending oppositely from the center plane of the plates in accordance with a uniform pattern and at a uniform height throughout the plates, said dimples being aligned in columns parallel to the longitudinal side edges of the plates and rows generally transverse thereto, the crests of the dimples in adjacent plates being in alignment and overlying each other, said dimples having inclined sides and flat tops and said flat tops of dimples on adjacent plates being in aligned spaced relationship, each dimple from one plate being in alignment with an oppositely extending dimple on the next adjacent plate, a set of parallel spacer strips secured to and extending across the tops of said dimples throughout the major portion of the extent of said plates, there being one strip for each row of dimples, said spacer strips of said set being graduated downwardly in thickness from a strip of greatest thickness which overlies the aligned dimples which lie near and next adjacent the periphery of the plates to a strip of least thickness which overlies the aligned dimples which lie at a position toward the center of said plates, said spacer strips terminating at positions spaced from the ends of said plates and said dimples on the one side of said portion of said plates extending from the ends of said strips to the ends of said plates being provided With spacer riders, said spacer riders including short strips of material extending in a direction transverse to the direction of said spacer strips, said strips of material forming said riders commencing at a position part way up the inclined sides of said dimples and terminating in a position overlying said flat tops of said dimples, said riders lying in columns and rows being secured to said dimples and said columns of riders dec easing in thickness from a position adjacent the periphery of said plate to the riders of least thickness at a position toward the center thereof.

'7. Flexible plate heat exchanger construction as in claim 6, said spacer strips and said riders lying in aligned relationship and said aligned strips and riders in each column having the same thickness.

References Cited by the Examiner UNITED STATES PATENTS 2,659,392 11/1953 Frenkel l65-166 FOREIGN PATENTS 74,761 9/ 1952 Denmark.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner. 

1. IN PLATE HEAT EXCHANGERS, A PLURALITY OF FLEXIBLE HEAT EXCHANGE PLATES OF SUBSTANTIALLY UNIFORM SIZE AND SHAPE, SAID PLATES BEING ASSEMBLED IN ALIGNMENT IN SPACED PARALLEL RELATIONSHIP AND FORMING SETS OF ALTERNATING CHANNELS FOR THE PASSAGE OF DIFFERENT MEDIA IN HEAT EXCHANGING RELATIONSHIP THERETHROUGH, SAID PLATES BEING FORMED WITH EMBOSSINGS PROVIDING A UNIFORM PATTERN OF ROWS OF PROJECTIONS EXTENDING A UNIFORM DISTANCE FROM OPPOSITE SIDES THEREOF, THE ROWS OF PROJECTIONS EXTENDING PARALLEL TO THE EDGES OF SAID HEAT EXCHANGER PLATES, MEANS FOR SECURING SAID PLATES TOGETHER WITH SAID EMBOSSINGS EACH PROJECTION FROM ONE PLATE BEING IN ALIGNMENT WITH AN OPPOSITELY EXTENDING PROJECTION ON THE NEXT ADJACENT PLATE, AND SPACER MEANS SECURED TO THE TOPS OF THE EMBOSSINGS IN THE ROWS THEREOF BORDERING THE EDGES OF SAID PLATES ON ONE SIDE OF EACH OF SAID PLATES, SAID SPACER MEANS OF SUCCESSIVE ROWS DECREASING IN THICKNESS IN THE DIRECTION FROM THE EDGE OF SAID PLATES TOWARD THE CENTER THEREOF. 